1. Field of the Invention
This invention is directed toward an improved boom construction incorporating a boom assembly.
The invention is more particularly directed toward an improved tree delimber machine having a boom assembly.
2. Description of the Prior Art
Tree delimber machines normally employ a long boom assembly mounted on a vehicle via an upright boom support. The boom assembly can comprise a boom slidably mounted through a sleeve. The outer end of the boom is equipped with tree gripping and delimbing means. The sleeve has tree gripping means at its front end. The boom support can be tilted forwardly on the vehicle by means of an extensible, rigid link pivotally connected between the boom support and the vehicle. Tilting the boom support lowers the front end of the boom, when it is extended from the sleeve, so it can pick up a tree lying on the ground by its butt end with the tree gripping means. The boom member is then withdrawn through the sleeve bringing the butt end of the tree with it until the butt end can be grasped by the tree gripping means on the sleeve. The tree gripping means on the boom then releases the tree and the boom is again moved forward to have the tree delimbing means on the boom delimb the tree while it is held by its butt end by the tree gripping means on the sleeve. The boom assembly and boom support are then operated to deposit the delimbed tree in the desired location preparatory to delimbing the next tree. This type of tree delimber machine is well known.
The tree delimber machines have the long boom assembly located relatively high above the ground when in the working position in order to function properly. However when the boom assembly is in the working position on the delimber machine, the delimber machine is not particularly suited for travelling from one work site to another. With the boom assembly located relatively high above the ground, the center of gravity of the machine is high making the machine relatively unstable and great care must be taken not to upset the machine during travel. While the boom support can be tilted forwardly with the extensible rigid link to lower the center of gravity of the machine, the rear end of the long boom assembly is raised during this operation making it impossible for the machine to pass under most bridges. Even without tilting the boom support forwardly, and thereby raising the rear end of the boom assembly, the machine is quite high and passage under many bridges is impossible. Also, the raised rear end of the boom assembly on the machine may exceed a legal height limit imposed on machines travelling on roads.
To move the tree delimber machines from one work site to another it was previously necessary to disconnect the boom assembly from the boom support. The boom support on the vehicle was lowered and both the vehicle and the disconnected boom assembly were moved to the new work site. At the new work site, the boom assembly was reconnected to the boom support and raised by the boom support to its working position. This operation however was time consuming and required additional lifting and handling apparatus.
It was then found that the tree delimber machine could more easily be placed in a transport mode by mounting the boom assembly to the boom support with hinge means. With the boom assembly pivotally mounted to the boom support, the boom support could be pivoted down relative to the vehicle while the boom assembly was being tilted upwardly relative to the boom support. This maintained the boom assembly generally parallel to the ground while both it and the boom support were being lowered so as to reduce the overall height of the machine. The boom assembly remained connected to the boom support. In the working position of the boom assembly, the boom assembly was locked to the boom support, usually with a plurality of bolts. However, when it was time to move the machine from one work site to another, the bolts were removed allowing the boom assembly to pivot relative to the boom support and allowing the boom assembly to be lowered without disconnecting it from the vehicle. With the machine now in a travel position, it was moved to a new work site. At the new work site, the boom support was raised back to an upright position thereby also raising the boom assembly. As the boom assembly was raised it pivoted relative to the boom support to maintain a generally parallel position to the ground. Once the boom support was fully raised to place the machine back in a working position the boom assembly was again locked to the boom support with the bolts. An example of the above machine is shown in Canadian Patent 1,116,053 by way of example.
While the above machine, employing a pivot connection between the boom assembly and the boom support, simplified moving the machine from one work site to another, there was still considerable work involved in locking and unlocking the boom assembly to and from the boom support. Also the relative movement of the boom assembly to the boom support while unlocked was difficult to control.
Another solution to setting up the machine in a travel position involved providing second extensible rigid link means pivotally connected between the boom support and the boom assembly. Normally with the boom assembly in the raised, working position the second link means is locked in place locking the boom assembly to the boom support. When it is desired to change the machine from a working mode to a travel mode however, the second link means is unlocked allowing it to extend and to pivot the boom assembly away from the boom support about the hinge means connecting them as the boom support is being lowered by the first link means. The second link means maintains the boom assembly generally parallel to the ground as the boom assembly is being lowered to a travel position. An example of this system is shown in Canadian Patent 1,275,027. This system places a great strain on the second link means however resulting in frequent maintenance and replacement of the second link means. Also, the second link means are mounted in an exposed position and are vulnerable to damage when the machine is working.